The evolution of integrated circuit (IC) fabrication technology has made possible the fabrication of microelectronic complexes, which perform a wide variety of functions and are characterized by varying degrees of complexity. Microelectronic complexes, that is systems and groups of discrete microelectronic functional modules, implement an important range of electronic devices, including microcomputers and microprocessors, and have important application in the design of electronic systems. Examples of such microelectronic complexes include semi-conductor wafers containing a plurality of chips or integrated circuits, as well as integrated circuits containing a plurality of microelectronic components.
In operation, a functional module of a microelectronic complex will heat up, and will require a certain amount of cooling in order to maintain acceptable operating conditions within the functional module and within the microelectronic complex. At the functional module level, cooling is required in order to prevent over-heating and subsequent malfunctioning or failure of, as well as possible damage to, the functional module. At the microelectronic complex level, cooling is required to minimize undesirable temperature differences between the functional modules, thus assuring an even temperature distribution across the microelectronic complex.
In the case of a semiconductor wafer including a plurality of integrated circuits, the discrete functional modules of the wafer are also referred to as cells. More specifically, a wafer is typically divided into a plurality of cells, each cell consisting of at least one integrated circuit. In operation, the different cells of the wafer may not all be operational at the same time, in which case the cells will not all heat up at the same time. Obviously, the cells that are in use will heat up more than the cells that are not in use, such that the cooling requirements for the wafer vary both as a function of time and location. A common problem in the field of semiconductor wafers is the creation of hot spots on the wafer where particular cells of the wafer generate an extreme amount of heat and do not receive adequate cooling. Such hot spots are characterized by excessive thermal expansion of the semiconductor material, and may lead to breakage in the semiconductor material.
One existing device for cooling microelectronic complexes is a temperature control structure, typically used to control the heating and cooling of specific regions of an integrated circuit chip. The temperature control structure includes multiple temperature control cells, formed on the chip surface by ion implanting N- and P-type dopant into adjacent regions, and then forming a metal bridge across similarly positioned ends of successive regions. A potential drop is applied across metal contacts of the cell, thus changing the temperature of the contacts relative to that of the electrically conducting bridge. Fabrication of arrays of temperature control cells of various shapes and sizes permits extremely precise heating and cooling of specific regions of the integrated circuit. Further, changing the type and/or concentration of conductivity-altering dopant present in a doped region, or changing the magnitude and/or polarity of the voltage drop across the metal contacts, will affect the character of the temperature control exerted.
Unfortunately, such a cooling device is quite complex and uses up an excessive amount of space on the body of the microelectronic complex, thus reducing the area available for processing elements. Further, the cooling device does not provide flexible control of the different temperature control cells during operation of the integrated circuit.
Another existing device is a cooling module including a plurality of cooling members, typically used to cool a plurality of integrated circuit chips mounted on a wiring substrate. Each cooling member is associated with a particular integrated circuit chip and is operative to cool that particular chip. Each cooling member has therein a space for circulating coolant, and is connected to neighboring cooling members by flexible pipes (bellows). The heat generated by an integrated circuit chip is conducted from the chip to its associated cooling member and cooled by the coolant circulating through the cooling member. The coolant circulates successively through cooling members arranged in the row or colum direction via the inter-connecting bellows.
Unfortunately, such a cooling module is inefficient in that cooling is provided to each integrated circuit chip successively, without discrimination or flexibility. Thus, cooling is provided to all of the integrated circuit chips, even those that are non-functional and not generating heat. Further, there is no differentiation in the amount of cooling provided to the integrated circuit chips on the basis of the specific cooling requirements of the chips.
Against this background, it clearly appears that a need exists in the industry for an improved method and apparatus for cooling microelectronic complexes.